Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
With conventional designs, a pitch bearing is assembled to the rotor hub for each respective rotor blade, with the root end of the blade bolted directly to the pitch bearing. The pitch bearing design is driven largely by the finite stiffness of the parts to which the bearing mates, particularly the blade root. The bearings deform less under load when the component they are attached to has a greater stiffness. For larger rotor designs, the pitch bearing design margins are often the parameter that dictates the blade root diameter. However, the root area of the blade contributes little to the efficiency of the blade and current blade radius of curvature design/manufacturing limits result in a relatively long spanwise transition from the relatively large root end to the thinner airfoil section of the blade. As such, as the wind turbines increase in size and output (with the corresponding increase in blade size), the cost of the rotor assembly increases as a function of pitch bearing design margins without a proportional increase in blade efficiency.
Accordingly, there is need for an improved bearing/blade root configuration that enables more cost effective rotor system designs and provides for a shorter span-wise transition from the root to the airfoil section of the blade without necessarily decreasing the overall spanwise length of the blades.